Neurological stimulators have been developed to treat pain, movement disorders, functional disorders, spasticity, cancer, cardiac disorders, and various other medical conditions. Implantable neurological stimulation systems generally have an implantable signal generator and one or more leads that deliver electrical pulses to neurological tissue or muscle tissue. For example, several neurological stimulation systems for spinal cord stimulation (SCS) have cylindrical leads that include a lead body with a circular cross-sectional shape and one or more conductive rings (i.e., contacts) spaced apart from each other at the distal end of the lead body. The conductive rings operate as individual electrodes and, in many cases, the SCS leads are implanted percutaneously through a needle inserted into the epidural space, with or without the assistance of a stylet.
Once implanted, the signal generator applies electrical pulses to the electrodes, which in turn modify the function of the patient's nervous system, such as by altering the patient's responsiveness to sensory stimuli and/or altering the patient's motor-circuit output. In SCS for the treatment of pain, the signal generator applies electrical pulses to the spinal cord via the electrodes. In conventional SCS, “low frequency” electrical pulses are used to generate sensations (known as paresthesia) that mask or otherwise alter the patient's sensation of pain. For example, in many cases, patients report paresthesia as a tingling sensation that is perceived as less uncomfortable than the underlying pain sensation.
In conventional SCS, the patient must first undergo a test (or “trial”) period to determine if they are responsive to the therapy before a permanent system is implanted. Responders are identified by meticulously programming multiple programs into an “external” patient-worn trial stimulator system, and instructing the patient to choose the most beneficial program for pain relief. Each of these multiple programs corresponds to stimulating a combination of two or more electrodes out of a total available set of 16 or more electrodes. Because paresthesia over large areas can result in discomfort for most patients, only a few electrodes are activated at a time in each program, to minimize the uncomfortable side effects for the patient. Also, amplitude changes are small and controlled in order to avoid shocking the patient. Typically, this trial testing is performed in and/or outside a clinic under the supervision of a trained practitioner.
In contrast to conventional SCS, a form of “high frequency” SCS has been developed that uses high frequency electrical pulses delivered to the spinal cord to treat the patient's sensation of pain without generating paresthesia or otherwise using paresthesia to mask the patient's sensation of pain. Thus, conventional deployment methods, which rely on paresthesia for feedback, may not be adequate for deploying high frequency SCS systems. Accordingly, there is a need for methods of deploying high frequency SCS systems that account for paresthesia-free therapy.